Agropyron Desertorum Research Articles

Effect of Water on Morphological Development in Seedlings of Three Range Grasses: Root Branching Patterns

Root morphology is important for successful seedling establishment and survival on semiarid rangelands. This study was conducted to determine the response of early seedling root morphological development of 'Hycrest' [Agropyron desertorum (Fisch. ex Link) Schult. X A. cristatum (L.) Gaert.], 'Whitmar' [Pseudoroegneria spicata (Pursh) Loeve], and cheatgrass (Bromus tectorum L.) to water. A greenhouse line-source sprinkler system provided a gradient of water application (77, 66, 37, and 5 ml/day). Root morphology was examined at 15, 30, and 45 days after seedling emergence. Order of branching of roots associated with the first foliar node was greater in cheatgrass than in Hycrest or Whitmar at all water applications and dates. Length of the primary root, length of the second group of seminal roots, and length of the first group of adventitious roots were similar in cheatgrass and Hycrest. Root branching for the 3 species decreased as less water was applied, except for cheatgrass irrigated with 5 ml/day. The ability of cheatgrass seedlings to grow with little water was related to their greater order of branching of seminal roots, branching density on the main axis, and length of lateral roots and external-external links. The greater root branching densities, lateral root lengths, and external-external link lengths enabled Hycrest seedlings to grow better than Whitmar seedlings with little water. These root morphological characteristics may prove useful in improving seedling establishment of perennial range grasses.

Influence of Temperature and Cheatgrass Competition on Seedling Development of Two Bunchgrasses

Rapid seedling growth and ability to compete against cheatgrass (Bromus tectorum L.) are 2 characteristics that perennial grasses must have for successful establishment on semiarid western rangelands. This study was conducted to determine the effects of temperature and competition from cheatgrass on seedling root and shoot growth of 'Hycrest' crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult. X A. cristatum (L.) Gaert.] and 'Whitmar' bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) Loeve). For the temperature study, seedlings were grown in growth chambers with alternate 12-h day/night temperatures of 10/5, 15/5, and 20/5 degrees C. Seedlings were destructively harvested on 6 dates and evaluated for 14 root and shoot characteristics. Leaf development, leaf area, total root length, and number and length of the second group of seminal roots were greater (P < 0.05) for cheatgrass than Hycrest and Whitmar at all dates and temperatures. Cheatgrass elongated adventitious roots earlier and at colder temperatures (10/5 degrees C) than Hycrest, and Whitmar did not produce adventitious roots at low temperatures. This would favor the establishment of cheatgrass at low temperatures. For the competition study, seedlings were established in pots in a greenhouse with planting ratios of Hycrest to cheatgrass and Whitmar to cheatgrass of 1:0, 2:0, and 5:0 (32, 64, and 159 plants m(-2) respectively) and compared with planting ratios of 1:1 and 1:4. Fourteen shoot and root characteristics were evaluated 15, 30, and 50 days after seedling emergence. Hycrest had greater shoot and root development than Whitmar for all seedling characteristics. Competition from cheatgrass reduced growth of Hycrest and Whitmar seedlings. At a planting ratio of 1:4, Hycrest-cheatgrass mixtures depleted soil moisture to lower soil water potentials than Whitmar-cheatgrass mixtures. These results indicate that Hycrest seedlings are more effective competitors with cheatgrass than Whitmar seedlings.

Root Morphological Development in Relation to Shoot Growth in Seedlings of Four Range Grasses

Successful seedling establishment in arid and semiarid rangelands depends on seedling root characteristics and on the relationship between shoot and root development. This study was conducted to determine seedling shoot and root developmental characteristics of 'Hycrest', a hybrid cultivar of crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult. X Agropyron cristatum (L.) Gaert.]; 'Whitmar', a cultivar of bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Love subspecies inermis (Scrib. and Smith) Love]; 'Secar', a cultivar of Snake River wheatgrass [Elymus lanceolatus (Scribner & J.G. Smith) Gould]; and cheatgrass (Bromus tectorum L.) under favorable growth conditions. Seedlings were grown in 20-cm X 20-cm pots filled with sandy loam soil in a greenhouse and were destructively harvested 9, 17, 24, 31, 39, and 45 days after emergence. Cheatgrass had greater (P<0.05) plant height, leaf area, total shoot dry weight, primary root length, number and order of branching of the second group of seminal roots, order of branching of the first group of adventitious roots, and total root dry weight than Hycrest, Whitmar, and Secar. Hycrest had greater (P<0.05) seedling growth than Whitmar and Secar. The pattern of root and shoot development was similar in the 4 species; however, species differed in the cumulative growing degree days required to initiate elongation and branching of siminal and adventitious roots. The close association between the pattern of root development and shoot growth in the 4 species may be useful in deriving models of root morphological development based on shoot development.

Salinity Resistance, Water Relations, and Salt Content of Crested and Tall Wheatgrass Accessions

Salinity is a significant factor in reducing stand establishment and productivity of grasses on certain rangeland sites. Research was undertaken to identify crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.] accessions potentially useful in breeding salt‐resistant populations and to determine physiological factors associated with the superior salinity resistance of tall wheatgrass [Thinopyrum ponticum (Podp.) Barkw. &amp; Dewey] compared to crested wheatgrass. Forage production under saline (irrigation with −0.6 MPa NaCI solution) and nonsaline conditions was examined in plants grown in sand culture. Consistent differences in forage salinity resistance (forage dry wt. of salinity stressed plants/forage dry wt. of unstressed plants) were not detected, but crested wheatgrass accessions were identified with both high salinity resistance at germination and high forage production under saline and nonsaline conditions. High forage‐producing crested wheatgrass accessions under salinity stress showed certain physiological responses similar to salt‐resistant tall wheatgrass. Tall wheatgrass and high producing crested wheatgrass maintained average leaf turgor of 1.0 MPa over a range of NaCI irrigation solutions from 0 to −1.8 MPa, but turgor of low‐producing crested wheatgrass was reduced by −1.2 and −1.8 MPa solutions. In −0.6 MPa solutions, tall wheatgrass and high forage‐producing crested wheatgrass accessions had higher concentrations of K, lower Na, and lower Na/K ratios in leaves than low‐producing crested wheatgrass. Concentrations of K, Na, and CI in root tissue did not differ in crested wheatgrass. Tall wheatgrass, however, had consistently higher root K, Na, CI, and lower Na/K ratios than crested wheatgrass. The results suggest that high forage production under saline conditions was related to turgor maintenance, lower Na/K ratios, and mechanisms for partial exclusion of Na in leaves.

PRODUCTION AND CYTOGENETIC STUDY OF INTERGENERIC HYBRIDS BETWEEN Triticum aestivum AND Agropyron desertorum

Through embryo culture, intergeneric hybrids were produced between common wheat, Triticum aestivum cv. Chinese Spring (CS) (2n= 6x = 42, AABBDD) and crested wheatgrass, Agropyron desertorum (2n =4x =28, PPPP) for the first time. Their F_2 and BC_1 seeds have also been successfully obtained by selfing and backcrossing with wheat in F_1 hybrids. The seedlings of all F_1 hybrids tended to resemble their female parent, but they had more tillers, and their spike characteristics were between their parents. Average meiotic chromosome pairing at MI of F_1 hybrids was: 6.62Ⅰ+ 8.20RingⅡ+ 4.16RodⅡ+0.57Ⅲ+ 0.35Ⅳ+0.06Ⅴ+ 0.03Ⅵ. The successful experience of hybridization of common wheat with A. desertorum, the reason for the high level of chromosome pairing and self-fertility in the F_1 hybrids were discussed. The F_2 and BC_1 seeds obtained in F_1 hybrids are of great importance to theory and practice.

Exploitation of Phosphate from Fertile Soil Microsites by Three Great Basin Perennials when in Competition

The effectiveness of phosphate (P) exploitation from fertile soil microsites was investigated with a dual-radioisotope approach for three perennial Great Basin species. Three experi- ments with competing species pairs assessed the ability to acquire P in fertilized and control patches. The patches occupied less than 1% 6fmthe rooted soil volume. In all experiments, the plants acquired at least as much radioisotope from the enriched as from the control patches even though the isotopes in the enriched patches were diluted by a factor of 108 with added 31P. The plants procured P from the enriched patches in propor- tion to its increased concentration relative to P in the control patches. The relative ability of the competing species to acquire P was very similar in control and enriched patches. Artemisia triden- tata (Rydb.) Beetle was able to acquire much more P than Pseudoroegneria spicata (Pursh) A. Lbve and was equivalent in ability to acquire P when in competition with Agropyron desertorum (Fisch, ex Link) Schult. However, when the Agropyron and Pseudoroegneria were together, they were unexpectedly similar in procuring P.

Effect of competition on stable carbon isotope ratios of two tussock grass species.

Previous studies have shown that plant carbon isotope composition varies when plants experience differences in water and nutrient availability. However, none have addressed the effect of root interactions, including competition for these soil resources, on carbon isotope ratios. We studied the effect of interspecific root interactions on the productivity and carbon isotope ratios of two Great Basin tussock grass species (Agropyron desertorum and Pseudoroegneria spicata). We compared grasses grown in mixture with sagebrush (Artemisia tridentara) to grasses in similar mixtures but where root interactions with sagebrush were limited by fiberglass partitions. During both years of the study, tussocks growing in competition with sagebrush produced tissue with more negative δ13C values than grasses experiencing limited root interaction with sagebrush. The magnitude of this difference (0.5 to 0.9%) is similar to that found in other studies when soil fertility and moisture availability were altered.

Carbon Isotope Discrimination and Water Use Efficiency in Four Cool‐Season Grasses

Carbon isotope discrimination (Δ) has been correlated with water use efficiency (WUE) in several C3 plant species and may be useful as a plant selection factor for improving WUE in crops. Research was undertaken to determine if differences in Δ could be found in grass accessions from the National Plant Germplasm System and if Δ of field grown plant tissue could be linked to WUE in greenhouse pots (pot WUE). Leaf Δ was measured on several accessions of Agropyron desertorum (Fischer ex Link) Schultes (standard crested wheatgrass), Festuca arundinacea Schreb. (tall fescue), Dactylis glomerata L. (orchardgrass), and Lolium perenne L. (perennial ryegrass). Accessions were established and grown under irrigated and dryland conditions at Central Ferry, WA and dryland conditions at Pullman, WA in the spring and summer of 1988. Differences in Δ among accessions within species were significant, but the environment by accession (within species) interaction was not, indicating that accession differences in Δ were generally consistent across environments. Measurements of pot WUE (dry weight/pot evapotranspiration) were made under greenhouse conditions on accessions of Dactylis, Festuca, and Lolium that had high and low field Δ and dry matter productivity. Accessions selected for low field Δ always had higher pot WUE based on shoot dry weight than high Δ selections under well‐watered and drought‐stressed conditions. This was also true of pot WUE based on whole‐plant dry weight in all cases except Festuca under drought‐stress. Accessions with low field Δ had higher water potential, solute potential, and turgor pressure than high Δ accessions in the greenhouse experiment, suggesting a more favorable water status for growth. The results link pot WUE with field Δ in a way consistent with theoretical expectations and suggest that Δ can be effectively used to evaluate C3 grass germplasm for WUE.

Impact of early root competition on fitness components of four semiarid species.

Plant demographic and root exclusion approaches were used to examine the influence of roots of adult Artemisia tridentata, Agropyron desertorum, and Agropyron spicatum individuals on seedling survival of four C3 semiarid species, three perennials, Ar. tridentata, Ag. desertorum, Ag. spicatum, and an annual, Bromus tectorum. Furthermore, height of Ar. tridentata seedlings and seed production of B. tectorum were assessed. The probability of a seedling being alive significantly depended on the seedling species, the neighboring adult species, and on the depth to which root competition was excluded. As seedlings, survival of Agropyron species did not differ, whereas survival of Ar. tridentata seedlings was higher than Ag. desertorum and was similar to Ag. spicatum. Bromus tectorum maintained significantly higher survival rates than perennial seedlings. Established individuals of Ar. tridentata reduced seedling survival more than established individuals of either Agropyron species. Seedling survival significantly increased with greater depth of root exclusion for the perennials but did not significantly affect seedling survival of B. tectorum. Height of Ar. tridentata seedlings and seed production of B. tectorum significantly increased with depth of root exclusion. Seed production of B. tectorum was highest when competing with Ag. desertorum and was lowest with Ar. tridentata. Root competition decreased the seed population of B. tectorum in the next generation even though it had no impact on survival. Competition in the upper soil horizon occurs between seedlings and established adults early in the growing season and potentially restricts root growth of seedlings. In arid and semiarid ecosystems, soil moisture is depleted from the upper horizons first, resulting in the death of seedlings that do not have access to moisture.

Survival and Growth of Globemallow [Sphaeralcea] Species in Dry Land Spaced-Plant Nurseries

Globemallows (Sphaeralcea spp.) have potential in rangeland seedings. Thirty-seven accessions of globemallow were grown at 2 sites in northern Utah and southern Idaho to quantify their agronomic attributes. Data for transplant survival, standing crop, and seed yield were collected in 1987 and 1988. Total globemallow survival (mean = 92%) and seed weights (mean = 0.8 g/plant) differed significantly (P?0.05) among locations. Plant weight (mean = 102 g/plant) differed significantly (P?0.05) among locations, species (S. grossulariifolia, S. coccinea, S. parvifolia, S. munroana, and interspecific hybrids), and years. In a second study, 5 globemallow accessions of 2 species and 'Spredor 2' alfalfa (Medicago sativa) were grown with 'Hycrest' crested wheatgrass (Agropyron desertorum X A. cristatum) to determine forage yields from 1985-1988. Globemallows produced significantly (P?0.05) less forage (62 g/m2) than alfalfa (389 g/m2). Forage yield of S. munroana (76 g/m2) did not differ significantly (P>0.05) from that of S. grossulariifolia (48 g/m2). Forage yield of crested wheatgrass (mean = 101 g/m2) did not differ significantly (P>0.05) when grown with globemallow versus alfalfa. Plant breeding and selection could probably improve these agronomic attributes for globemallows seeded on rangelands.

Root Length, Leaf Area, and Biomass of Crested Wheatgrass and Cheatgrass Seedlings

Cheatgrass (Bromus tectorum L.) dominates large tracts of rangeland in the western United States. Previous research has demonstrated the competitive nature of this species; however, the mechanisms contributing to its dominance have not been well elucidated. It is often suggested that cheatgrass outcompetes perennial seedlings because it germinates and grows at lower soil temperatures. However, even in studies where temperatures are not limiting, cheatgrass outcompetes perennial seedlings. Therefore, I conducted a study to compare accumulation of root length, leaf area, and biomass of cheatgrass and crested wheatgrass (Agropyron desertorum (Fisch. ex Link) Schult. cv. Nordan) seedlings under non-limifting conditions. Seedlings were grown in pots in the greenhouse for 60 days post-sowing. There were 4 seedlings per pot, and sampling was conducted weekly at 24-60 days after sowing. Maximum and minimum temperatures were 28? C and 40 C, respectively, and plants were watered twice a week. Cheatgrass had greater root length density and leaf area than crested wheatgrass, especially during the later samplings. For the last 2 samplings, cheatgrass averaged about 12% more root mass and 56% more shoot mass, yet had more than twice the root length and leaf area of crested wheatgrass. Cheatgrass was more efficient (per unit of biomass) in producing leaf area and root length, which helps explain its ability to quickly become established and exploit soil nutrient and moisture reserves.

An interspecific hybrid and amphiploid produced from Triticum aestivum crosses with Agropyron cristatum and Agropyron desertorum

Agropyron cristatum L. Gaertner (2n = 14) and Agropyron desertorum (Fisch. ex Link) Schultes (2n = 28) cultivars were crossed with common wheat (Triticum aestivum L. em. Thell. 2n = 42, ABD genomes) in an attempt to bring the P genome of Agropyron into a wheat background for future genetic exploitation and to evaluate possible homoeology with the wheat genomes. Interspecific hybrid plants were obtained from crosses using both Agropyron species. Chromosome doubled amphiploids (2n = 56, AABBDDPP) were successfully produced by colchicine treatment of hybrid plants from the T. aestivum – A. cristatum cross. Meiotic cells of the amphiploid contained the expected 28 chromosome pairs but also exhibited a considerable amount of chromosome pairing disturbance, resulting in an average of 3.55 univalents per cell. Consequently, fertility was reduced in the amphiploid and the progeny were frequently aneuploid. Homoeologous pairing in the T. aestivum – A. cristatum hybrid was low, but the pairing disruption exhibited in the amphiploid suggested that homoeologous relationships may have been masked in the hybrid.Key words: Triticum aestivum, Agropyron cristatum, chiasma frequency, intergeneric hybrid, amphiploid.

The effect of clipping and water stress on the production of selected grass species in the Yemen Arab Republic

Four grass species were examined for their response to clipping and water stress in the Yemen Arab Republic (Y.A.R.). Andropogon distachyos L., Tetrapogon villosus Desf. and Themeda triandra Forssk. are native to the Y.A.R. while Agropyron desertorum (Fisch. ex Link) Schult. is an introduced species and was included for comparison. Plants were clipped to 1·5 cm at 3- or 6-week intervals and soil moisture was kept near field capacity or 30% of field capacity. Results indicated that T. villosus tolerated defoliation in combination with water stress better than the other native grass species. T. triandra seemed to be the least tolerant to clipping, whereas A. distachyos was intermediate.

SALINITY AND GERMINATION IN Agropyron desertorum ACCESSIONS

Salinity is an important factor limiting germination and emergence of crested wheat-grass [Agropyron desertorum (Fisch. ex Link) Schult.] on desert range sites. The objectives of this research were to examine germination characteristics of A. desertorum on saline media and to identify accessions with high salinity resistance at germination. Reductions in percent germination by NaCl solutions was relatively small between 0 and −0.6 MPa (92 to 85%), but more pronounced between −0.6 and −1.5 MPa (85 to 26%). Germination rate index (GRI) and maximum germination rate d−1 declined linearly from 0 to −1.5 MPa. Seventy-one accessions were evaluated for salt resistance in NaCl at −0.9 MPa. Accessions were identified with high relative germination (percent germination at −0.9 MPa divided by the distilled water controls) and high percent germination and GRI at −0.9 MPa. In most cases, accessions with high salt resistance, determined as high relative germination or percent germination at −0.9 MPa, were the same accessions with high relative GRI or GRI at −0.9 MPa. Maximum germination rate d−1 did not consistently identify salinity resistant accessions. Separation of high and low salt resistant accessions observed at 22 °C and −0.9 MPa for relative germination and GRI was also observed at −1.5 MPa, but not at −0.3 MPa. Separation of accessions with high and low salinity resistance was maintained at alternating daily temperatures of 15 °C (16 h)/25 °C (8 h), and at 12 °C constant temperature. In some cases, CaCl2 solutions at −0.9 MPa inhibited germination more than NaCl at −0.9 MPa. However, accessions showing differences in salt resistance on NaCl solutions showed the same qualitative separation on CaCl2 and in 1:1, NaCl:CaCl2 solutions. Accessions potentially useful for improving germination under saline conditions were identified and are available for field testing and further selection.Key words: Crested wheatgrass, plant stress resistance, salinity, salinity resistance

Field Populations of the Russian Wheat Aphid (Homoptera: Aphididae) and Other Cereal Aphids on Cool-Season Perennial Grass Accessions

Six species of cereal aphids infested field plots of perennial grass accessions of Festuca arundinacea Schreb. (tall fescue), Agropyron desertorum (Fisch. ex Link) Schultes (standard crested wheatgrass), and Dactylis glomerata L. (orchard grass) at Pullman and Central Ferry, Wash., in summer 1988. Seed of cool-season perennial grass accessions from the United States germplasm collection is routinely increased at Pullman and Central Ferry, Wash. Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera: Aphididae), assumed dominant status at Central Ferry and English grain aphid, Macrosiphum avenae (F.), was dominant at Pullman. Other species found were Metopolophium dirhodum (Walker), greenbug, Schizaphis graminum (Rondani), bird cherry-oat aphid,Rhopalosiphum padi (L.), and Sipha elegans del Guercio. Overall, aphid densities were highest in nonirrigated plots at Pullman (x aphids/five tillers = 191.87), intermediate in irrigated plots at Central Ferry (x = 47.86), and lowest in non irrigated plots at Central Ferry (x = 15.70). At Central Ferry, significantly fewer (P 0.05) aphids were recovered from F. arundinacea, than from A. desertorum and D. glomerata; however, aphid densities were higher on F. arundinacea at Pullman. Results indicate that cereal aphids pose a potential hazard to seed regeneration and should be monitored to ensure against loss of grass germ plasm. Also, results show that some commonly occurring Pacific Northwest perennial grasses have the potential to support natural populations of the Russian wheat aphid.

Comparative demography of co-occurring introduced and native tussock grasses: persistence and potential expansion

Demographic characteristics associated with the maintenance and growth of populations, such as seed dynamics, seedling emergence, survival, and tiller dynamics were examined for two tussock grasses, the native Agropyron spicatum and the introduced Agropyron desertorum in a 30-month field study. The introduced grass was aerially sown onto a native grassland site. Seed production of the introduced grass was greater than the native grass in both above- and below-average precipitation years. Seeds of A. spicatum were dispersed when they mature, while A. desertorum retained some seeds in inflorescences, and dispersed them slowly throughout the year. This seed retention allowed some seeds of the introduced grass to escape peak periods of seed predation during the summer and allowed seeds to be deposited constantly into the seed bank. Carryover of seeds in the seed bank beyond one year occurred in the introduced grass but not in the native species. For both species, seedling emergence occurred in both autumn or spring. Survival rates for A. desertorum were higher than A. spicatum when seedlings emerged between November and March. Survival rates of cohorts emerging before November favored A. spicatum whereas survival rates did not differ between species for cohorts emerging after March. Individuals of both species emerging after April were unable to survive the summer drought. Demographic factors associated with seeds of A. desertorum seemed to favor the maintenance and spread of this introduced grass into native stands formerly dominated by A. spicatum.

Carbon Isotope Dicrimination: Potential in Screening Cool‐Season Grasses for Water‐Limited Environments

Carbon isotope discrimination (∆) has been shown to be negatively related to water use efficiency (WUE) in several C3 crop species and has been proposed as a criterion to select for improved WUE in plant breeding programs. This study was conducted to determine if ∆ is related to WUE in crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes] and AItai wildrye [Leymus angustus (Trin.) Pilger] and to evaluate the influence of drought on the magnitude of genetic variability and broad‐sense heritability of ∆ among clones of crested wheatgrass. In a greenhouse pot experiment, ∆ was negatively related to WUE in crested wheatgrass (r = −0.73**, significant at P &lt; 0.01) and Altai wildrye (r −0.81**). In field studies, a line‐source sprinkler system operated in conjunction with an automated rainout shelter imposed a continuously variable water application on 29 vegetatively propagated clones of crested wheatgrass. Three water levels along the water application gradient were selected for sampling and forage dry weights and ∆ values were determined for two harvests in 1986 and one harvest in 1987. In the field experiment, ∆ declined as less water was applied and was positively associated with forage yield at each of the three harvests (r = 0.59**, 0.44**, and 0.80**, respectively). Significant variability for ∆ was detected among the clones for the two peak‐season harvests, hut not for the late‐season harvest in 1986. Broad‐sense heritability for ∆ was 0.49 in the analysis of data combined over harvests and water levels. Genetic variances and broad‐sense heritabilities (H) for ∆ were generally greater at the high (H = 0.52) and intermediate (H = 0.52) water applications than at the low water application (H = 0.37), and coefficients of variation for ∆ were typically less than 4.5%. Selection for ∆ appears to be a promising screening tool for the development of crested wheatgrass populations that are productive and make efficient use of limited water resources.

Oligosaccharides in foliage of Agropyron, Bromus, Dactylis, Festuca, Lolium and Phleum*

SUMMARYTemperatures are frequently too cool on rangelands of the western United States for plant growth to occur during much of the time when soil moisture is most readily available. Altering plant metabolism to facilitate growth under cool temperatures holds considerable potential for improving forage production on these ranges. Sucrosyloligosaccharides in representative grasses were characterized. Sucrosyloligosaccharides facilitate the partitioning of carbohydrates outside the chloroplasts during growth at cool temperatures. Eight grasses (Bromus inermis Leys., B. tectorum L., Dactylis glomerata L., Lolium perenne L., Festuca arnndinacea Schreb., Phleum pratense L., and two accessions of ‘Hycrest’ a cross between Agropyron desertorum (Fischer ex. Link) Schultes and A. cristatum L. Gaertner were grown in controlled environments at 10/5 ± 1 °C day/night temperatures. Oligosaccharides extracted from lyophilized leaves were separated using anion exchange chromatography. The relative amounts and kinds of trisaccharides varied among species. All grass contained both raffinose and 1‐ketose. Neoketose was the dominant trisaccharide in Lolium and Festuca but was absent from both Agropyron hybrids. 6‐Kestose was present in all species except L. perenne. Extracts of L. perenne and F. arundinacea contained a trisaccharide containing glucose, fructose and galactose (1:1:1), tentatively given the trivial name ‘loliose’. The oligosaccharide pattern in L. perenne, both Bromus species, D. glomerata and P. pratense suggest the presence of simple polymeric fructan series. However, the series are different from the inulin series in Jerusalem artichoke tubers. In contrast, chromatograms of leaf extracts of F. arundinacea and both Agropyron accessions have complicated profiles which may reflect the presence of both linear and branched polymers in those species. The oligosaccharide profiles determined by anion exchange chromatography may have useful chemotaxonomic applications.

Genetic Variances for Forage Yield in Crested Wheatgrass at Six Levels of Irrigation

Rangelands in the western USA are characterized by extreme seasonal and site variations in soil moisture and extended periods of severe water deficit. Development of improved germplasm that is productive over a wide range of soil moisture conditions is a major objective of forage breeding programs in this region. Ample levels of heritable genetic variation are prerequisites for genetic progress in any breeding program. Although expression of genetic variability among breeding lines is known to decrease in some species as water becomes limited, neither this relationship nor the stability of genetic responses at different water levels have been studied in crested wheatgrass, Agropyron desertorum (Fisch. ex Link) Schult. A linesource sprinkler system was used under a field rainout shelter to evaluate the dry matter yield of 29 clonal lines of crested wheatgrass at six levels of water application. Forage yield declined linearly from optimum water levels to levels representative of severe drought. Broad‐sense heritability values along with the range and genetic variance among clonal lines also declined markedly as water application decreased. Experimental error, as reflected by the coefficient of variation, was substantially larger under drought than at higher water applications. Although the clone ✕ water level interaction was significant (P &lt; 0.01), positive and significant (P &lt; 0.01) Spearman correlation coefficients indicated a relatively high degree of consistency among clones at different water application levels. Results indicate that this tetraploid population of crested wheatgrass has sufficient genetic stability to permit selection for forage dry matter yield at water levels substantially above the target level.

The effects of the spatial pattern of defoliation on regrowth of a tussock grass : III. Photosynthesis, canopy structure and light interception.

The spatial pattern of foliage removal from a tussock grass can influence regrowth through effects on daily carbon gain (CERd). This field study examined the extent to which tussock photosynthetic responses to different defoliation patterns were associated with changes in whole-canopy attributes (e.g., foliage age structure, canopy light microclimate). During the spring growing season, 60% of the green foliage area was removed from individual Agropyron desertorum tussocks with scissors in different spatial patterns. These patterns represented extremes of defoliation patterns that might be inflicted by natural herbivores. Tussock photosynthesis (per unit foliage area) at high light (2000 μmol photons m-2 s-1 between 400 and 700 nm; P2000) increased following clipping with all defoliation patterns. The increases in P2000 were greater when leaves were removed from low in the tussock (older leaves) than if leaves high in the canopy (younger leaves) were removed. These relative changes of P2000 among clipping patterns paralleled the responses of CERd and regrowth from an earlier study. Furthermore, the changes in P2000 corresponded with increases in the proportion of foliage within the tussocks that was directly illuminated at midday. The greater photosynthesis of tussocks after lower-leaf removal was directly related to a higher proportion of younger foliage and a smaller fraction of foliage shaded within the tussock. In a dense canopy, such as these grass tussocks, the influence of defoliation on whole-canopy attributes may be of primary importance to whole-plant photosynthetic responses.